If you are using MySQL as a service which is how XAMPP installs it then just use the control panel and go to admin, if you some how ran the command line see if the little redlight thing is in your system trey, when in the XAMPP control panel go to phpMyAdmin and see if you can connect through that.
Then if all that fails then find the original install program first then make sure it is in a different folder like the tmp folder then uninstall and reinstall XAMPP and it will set everything all up again. If you do want to run mysql from the command line after reinstall then go to the mysql folder and run the dos programs again. After uninstall before you reinstall make sure you delete all the MySQL files.
Port 80 is your web server and port 3306 is the MySQL port so it is not your MySQL.